There is a known amplification apparatus having a solid state power amplifier (SSPA) for providing amplification capability of RF signals, which may be used in place of magnetron oscillators having a magnetron as an oscillator/amplifier element. A typical such SSPA based amplification apparatus has: a signal splitter for splitting an RF signal into a plurality of split RF signals; a plurality of amplifier units for amplifying the split RF signals, respectively; and a signal combiner for combining the amplified RF signals together into a combined output RF signal. This structure is desirable because so high an output power level is required while a sole amplifier unit has only a limited capacity. Advantages of SSPA based amplification apparatuses in comparison to magnetron oscillators are a longer operational life and a higher easiness in maintenance.
As a related technique, a power amplification apparatus is known from Patent Document No. 1 listed below (Japanese Unexamined Patent Application Publication No. Hei-6-152278 (1994-152278)), which has: a power splitter and a power combiner disposed facing to each other; and a plurality of amplifier units disposed between the power splitter and the power combiner.